Flat-folded, multi-plate electrode assembly

ABSTRACT

A multi-plate wound cell assembly constructed similar to a conventional jellyroll electrode assembly except that each electrode comprises a series of plates spaced along a continuous current collector, and the plates are flat-folded rather than wound into a cylinder, is described. The length of the current collector between adjacent plates of the anode and cathode electrodes increases as the folding progresses to allow for the increase as the electrode assembly is flat-folded.

BACKGROUND OF THE INVENTION

1. Field Of Invention

The present invention generally relates to the art of electrochemicalenergy, and more particularly, to a unique flat-folded, multi-plateelectrode assembly that is generally applicable to energy storagedevices of non-cylindrical or non-jellyroll configurations.Advantageously, the flat-folded, multi-plate electrode design of thepresent invention reduces the number of individual components and thenumber of mechanical connections required between the anode and cathodeelectrodes and their respective battery terminals. In that manner, thepresent invention simplifies the assembly process in a multi-plateelectrochemical power source and is adaptable in a wide variety ofelectrode configurations and shapes for such applications as capacitorsincluding electrolytic capacitors, ceramic capacitors, foil capacitors,super capacitators, double layer capacitators, and batteries includingaqueous and nonaqueous primary and secondary batteries.

2. Prior Art

Wound batteries are a typical electrode configuration formed of acontinuous anode and a continuous cathode assembly laid one on top ofthe other and wound into a jellyroll. Such an electrode configuration isdesirable because the continuous anode and cathode electrodes require aminimal number of mechanical connections to their respective terminalleads, and the jellyroll assembly is generally recognized as preferredfor high discharge and current pulse applications.

However, in some applications, a cylindrically shaped electrode assemblyis not desired. Instead, a battery is required that fits inside of acasing having at least two spaced apart and planar side walls joined byend walls. Such prismatic shaped casings are commonly used to housemulti-plate battery assemblies. A typical multi-plate battery assemblyconsists of a series of individual cathode plates inserted between anaccordion folded, continuous anode in electrical contact with thecasing. The cathode plates are then joined mechanically, such as bywelding a series of leads to each of them and then connecting the leadsto a bus. Not only does the typical multi-plate battery assembly requiremany individual components but the assembly process can be very timeconsuming.

What is needed is a multi-plate electrode assembly that includes many ofthe desirable features of the jellyroll wound configuration such asunitary anode and cathode electrodes, but that is provided in a shapethat can be housed inside of a prismatic casing. The flat-folded,multi-plate electrode assembly of the present invention provides theseadvantages.

SUMMARY OF THE INVENTION

The flat-folded, multi-plate electrode assembly of the present inventionis intended to be housed inside of a prismatic case and includes anodeand cathode active materials supported on respective current collectors.The current collectors are preferably continuous, but may be formed ofsegments joined together to form a unitary member. The active materialsof each electrode are provided as discrete portions spaced from eachother at progressively increasing intervals along the length of therespective current collectors. The intermediate portions of the currentcollectors devoid of active materials allow for the increase in cellthickness from the center to the outside of the assembly as theelectrodes, separated by an insulating material, are aligned and thenflat-folded along their length. The resulting multi-plate electrodeassembly according to the present invention insures that active materialinterface between the electrodes occurs over the largest availablesurface. Integral tabs extend from each of the electrode currentcollectors for anode to case and cathode to terminal lead connection.There can be single or multiple leads depending on electricalrequirements and battery configuration.

The foregoing and additional advantages and characterizing features ofthe present invention will become clearly apparent upon a reading of thefollowing detailed description together with the included drawings.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a plan view of the anode 12, cathode 14 and separator 16before beginning of the assembly operation.

FIG. 2 is a side elevational view showing the first fold in the assemblyoperation.

FIG. 3 is a side elevational view of a partially assembled electrodeassembly 10 according to the present invention.

FIG. 4 is a side elevational view of the finished flat-folded electrodeassembly according to the present invention.

FIG. 5 is a perspective view of the flat-folded electrode assembly 10showing the orientation of the anode tabs 28,30 and the cathode tab 40.

DETAILED DESCRIPTION OF THE INVENTION

Turning now to the drawings, FIGS. 1 to 5 show an electrode assembly 10(FIG. 4) according to the present invention comprised of an anodeelectrode, generally indicated at 12, a cathode electrode, generallyindicated at 14 and a separator 16 positioned between the anode and thecathode to prevent short circuit contact therebetween. Anode electrode12 comprises a continuous, elongated element or structure, preferably ofan anode active material such as an alkali metal provided in the form ofplates 18A to 18G supported on contact portions (not shown) of aconductive member 20 serving as an anode current collector. Preferablythe anode active material is contacted to both sides of the anodecurrent collector 20.

Each of the anode plates 18A to 18G is generally in the shape of arectangular sheet of the alkali metal having a step 22A to 22G providedat one of the plate corners. However, those skilled in the art willreadily recognize that the rectangular shape is not necessary and that amyriad of other shapes for the anode plates are contemplated withoutdeparting from the scope of the present invention. In the presentembodiment of the anode electrode 12, the step 22A of the first anodeplate 18A faces the step 22B of the second anode plate 18B with theopposite edge 24A of the second plate facing the edge 24B of the thirdanode plate 18C. This pattern is repeated along the anode electrode 12from the anode plates 18A to 18F. The last anode plate 18G has its edge24F facing the edge 24E of plate 18F.

The anode current collector 20 is comprised of a conductive materialsuch as of a conductive screen and the like having a shape similar tothat of the anode plates 18A to 18G with anode connector portions 26A or26E bridging between adjacent plates. The anode connector portions arepreferably integral with the contact portions of the anode currentcollector 20 supporting the various anode plates. In particular, theanode current collector 20 includes the first anode connector portion26A bridging between the contact portions supporting anode plates 18Aand 18B. The first anode connector portion 26A is spaced from the steps22A and 22B. The second anode connector portion 26B bridges between thecurrent collector contact portions supporting anode plates 18B and 18Cand in line with the first anode connector portion 26A. The third anodeconnector portion 26C bridges between the contact portions of the anodecurrent collector supporting plates 18C and 18D, directly proximate therespective steps 22C and 22D. A fourth anode connector portion 26Dbridges between the contact portions of the current collector supportinganode plates 18D and 18E and in line with the first and second anodeconnector portions 26A, 26B. A fifth anode connector portion 26E bridgesbetween the current collector contact portions supporting anode plates18E and 18F, directly proximate the respective steps 22E and 22F.Finally, a sixth anode connector portion 26F bridges between the contactportions of the anode current collector supporting plates 18E and 18F,and in line with the first, second and fourth anode connector portions26A, 26B and 26D. The anode electrode 12 is further provided with afirst tab 28 extending from the current collector adjacent to the step22F of the fifth plate 18F and a second tab 30 adjacent to the step 22Gof the seventh plate 18G.

While the tabs 28, 30 are shown extending along the longitudinal axis ofthe current collector, that is not necessary. There can be connectortabs extending from any one of the anode plates 18A to 18G, and the tabscan extend in both a horizontal and/or a vertical direction, as desired.At the least, one tab is required for connection to the anode terminal.

In the present embodiment, the connector portions 26A to 26E are of areduced width as compared to that of the contact portions supporting theanode active material. This helps to conserve space inside the casingfor active materials. In an alternate embodiment of the presentinvention, the connector portions extend the entire width of the currentcollector.

It will be apparent to those skilled in the art that while the anodeelectrode 12 is shown comprised of seven plates supported on respectivecurrent collector contact portions joined together by the intermediateconnection portions, that is for illustrative purposes only. In thatrespect, the anode 12 can be comprised of the current collector 20having a greater or a lesser number of contact portions supportingrespective anode plates than the exemplary seven plates shown.

According to the present invention, the length of the sixth connectorportion 26F is somewhat greater than that of the fifth connector portion26E which in turn is somewhat greater than the length of the fourthconnector portion 26D which is somewhat greater in length than that ofthe third connector portion 26C which is somewhat greater in length thanthat of the second connector portion 26B which in turn is somewhatgreater in length than that of the first connector portion 26A. Therelationship between the lengths of the various connector portions willbe explained in greater detail hereinafter.

In a similar manner as the anode electrode 12, the cathode electrode 14is a continuous structure provided with plates 32A to 32F of activematerial contacting a conductive member 34 serving as a cathode currentcollector. The cathode plates 32A to 32F are preferably of a metal, ametal oxide, a metal sulfide, a mixed metal oxide or a carbonaceousmaterial, and are generally in the shape of rectangles provided withrespective steps 36A to 36F. The cathode plates are sized and configuredto overlay the second to the seventh anode plates 18B to 18E. As withthe anode plates 18A to 18G, the rectangular shape is not required,however, the shape of the respective anode and cathode plates must besimilar so that when the electrodes are laid one on top of the other,they substantially cover each other. The cathode current collector 34 iscomprised of a conductive material such as of a conductive screen andthe like having a shape similar to that of the cathode plates 32A to 32Fwith cathode connector portions 38A to 38E bridging between adjacentplates. The cathode connector portions are preferably integral with thecontact portions (not shown) of the cathode current collector 34supporting the various cathode plates.

In particular, the cathode current collector 34 includes the firstcathode connector portion 38A bridging between the contact portionssupporting cathode plates 32A and 32B. A step 36A and an adjacent tab 40extend from the opposite side of the cathode plate 38A. A second cathodeconnector portion 38B bridges between the current collector contactportions supporting cathode plates 32B and 32C, spaced from respectivesteps 36B and 36C facing each other. A third cathode connector portion38C bridges between the contact portions of the cathode currentcollector supporting plates 32C and 32D and in line with the firstcathode current connector portion 38A. A fourth cathode connectorportion 38D bridges between the contact portions of the currentcollector supporting cathode plates 32D and 32E, spaced from respectivesteps 36D and 36E facing each other and in line with the second cathodeconnector portion 38B. Finally, a fifth cathode connector portion 38Ebridges between the contact portions of the cathode current collectorsupporting plates 32E and 32F in line with the first and third connectorportions 38A, 38C. A step 36F is provided in the sixth cathode plate32F, opposite the fifth connector portion 38E.

As is the case with the anode electrode 12, the cathode connectorportions 38A to 38E of the cathode electrode 14 are preferably of areduced width as compared to that of the contact portions supporting thecathode active material. This helps to conserve space inside of thecasing for active materials. Also, there can be more cathode tabs thantab 40 shown, and the tabs can extend from the current collector 34 ineither a vertical or a horizontal orientation, as desired.

Separator sheets 16 (only one shown in FIG. 1) are provided having aconfiguration and shape sized somewhat larger than that of the cathode14 including the connector portions extending between the cathodeplates. That way, the separator sheets 16 are positioned on either sideof the cathode and heat sealed or otherwise joined about theirperipheries to completely envelope the cathode 14.

As shown in FIG. 2, the separator enveloped cathode 14 is thenpositioned overlaying the anode 12 beginning at the second anode plate18B. In that manner, the first cathode plate 32A covers the second anodeplate 18B, the second cathode plate 32B covers the third anode plate18C, the third cathode plate 32C covers the fourth anode plate 18D, thefourth cathode plate 32D covers the fifth anode plate 18E, the fifthcathode plate 32E covers the sixth anode plate 18F and the sixth cathodeplate 32F covers the seventh anode plate 18G.

With the cathode 14 thus overlaying the anode 12, the various cathodeconnecting portions 38A to 38E are offset or spaced from the respectiveanode connecting portions 26B to 26F. Then, the first anode plate 18A isfolded up, as indicated by arrow 42, and over the first cathode plate32A, as indicated by arrow 44, so that the first cathode plate 32A isdisposed intermediate the first and second anode plates 18A, 18B to forma first sandwich configuration 46 (FIG. 3). According to the presentinvention, the first anode connector portion 26A has a length onlysomewhat greater than the thickness of the first cathode plate 32A toallow for the flat-folded anode/cathode/anode sandwich configuration 46.As indicated by arrow 48, the first sandwich configuration 46 is thenflat-folded onto the second cathode plate 32B overlaying the third anodeplate 18C to form a second sandwich configuration (not shown) having thesecond anode plate 18B overlaying the first cathode plate 32A which inturn overlays the first anode plate 18A overlaying the second cathodeplate 32B which in turn overlays the third anode plate 18C. In thatmanner, the second anode connector portion 26B and the first cathodeconnector portion 38A are of a similar length somewhat greater than thethickness of the first sandwich configuration 46 to thereby provide thesecond sandwich configuration. As indicated by arrows 50 to 56 in FIG.3, this flat-folding pattern is continued until the anode 12 and thecathode 14 have been completely folded upon themselves to provide theflat-folded, multi-plate electrode assembly 10 shown in FIG. 4.

According to the present invention, the length of the various anodeconnectors 26A to 26F and the length of the various cathode connectors38A to 38E increase along the extent of the anode 12 and the extent ofthe cathode 14 from their respective first plates 18A, 32A to their lastplates 18G, 32F to accommodate the progressively increasing flat-foldedthickness of the electrode assembly 10, as indicated by arrows 48 to 56.Thus, the completed flat-folded electrode assembly 10 shown in FIG. 4comprises the following electrode plate sequence moving from the top ofthe drawing down: anode plate 18F/cathode plate 32E/anode plate18D/cathode plate 32C/anode plate 18B/cathode plate 32A/anode plate18A/cathode plate 32B/anode plate 18C/cathode plate 32D/anode plate18E/cathode plate 32F/anode plate 18G.

FIG. 5 shows the position of the anode tabs 28,30 and the intermediatecathode tab 40 of the completed, flat folded electrode assembly 10intended to be housed inside of a conductive casing (not shown),preferably of a prismatic shape. The anode tabs are provided forconnection to the conductive casing while the cathode tab is positionedfor connection to the terminal lead (not shown) in a typicalcase-negative cell design, which is the preferred construction for thecell of the present invention.

By way of example, in an illustrative battery according to the presentinvention, the anode active material is an alkali metal selected fromGroup IA of the Periodic Table of Elements and contacted to a nickelcurrent collector, and the cathode active material is of a carbonaceousmaterial, fluorinated carbon, metal, metal oxide, mixed metal oxide or ametal sulfide, and mixtures thereof. Preferably, the cathode material ismixed with a conductive diluent such as carbon black, graphite oracetylene black or metallic powders such as nickel, aluminum, titaniumand stainless steel, and with a fluoro-resin powder binder material suchas powdered polytetrafluroethylene or powdered polyvinylidene fluoride.The thusly prepared cathode active admixture is contacted to the cathodecurrent collector which is a thin sheet or metal screen, for example, atitanium, stainless steel, aluminum or nickel screen.

The separator is of electrically insulative material, and the separatormaterial also is chemically unreactive with the anode and cathode activematerials and both chemically unreactive with and insoluble in theelectrolyte. In addition, the separator material has a degree ofporosity sufficient to allow flow therethrough of the electrolyte duringthe electrochemical reaction of the cell. Illustrative separatormaterials include woven and non-woven fabrics of polyolefinic fibers orfluoropolymeric fibers including polyvylidine fluoride,polyethylenetetrafluoroethylene, and polyethylenechlorotrifluoroethylenelaminated or superposed with a polyolefinic or a fluoropolymericmicroporous film. Suitable microporous films include apolytetrafluoroethylene membrane commercially available under thedesignation ZITEX (Chemplast Inc.), polypropylene membrane commerciallyavailable under the designation CELGARD (Celanese Plastic Company, Inc.)and a membrane commercially available under the designation DEXIGLAS (C.H. Dexter, Div., Dexter Corp.). The separator may also be composed ofnon-woven glass, glass fiber materials and ceramic materials.

The exemplary battery of the present invention having the flat-foldedelectrode assembly is activated with an tonically conductive electrolytewhich serves as a medium for migration of ions between the anode and thecathode electrodes during the electrochemical reactions of the cell. Theelectrochemical reaction at the electrodes involves conversion of ionsin atomic or molecular forms which migrate from the anode to thecathode. Thus, electrolytes suitable for the present invention includeboth aqueous and nonaqueous solutions that are substantially inert tothe anode and cathode materials, and that exhibit those physicalproperties necessary for ionic transport, namely, low viscosity, lowsurface tension and wettability.

By way of example, a suitable electrolyte for an alkali metal activeanode has an inorganic or organic, ionically conductive salt dissolvedin a nonaqueous solvent, and more preferably, the electrolyte includesan ionizable alkali metal salt dissolved in a mixture of aprotic organicsolvents comprising a low viscosity solvent and a high permittivitysolvent. The ionically conductive salt serves as the vehicle formigration of the anode ions to intercalate or react with the cathodeactive material. Preferably the ion-forming alkali metal salt is similarto the alkali metal comprising the anode.

The preferred form of the flat-folded electrode assembly of the presentinvention is a case-negative design wherein the anode/cathode couple isinserted into a conductive metal casing such that the casing isconnected to the anode current collector via anode tabs 28 and 30 (FIG.5), as is well known to those skilled in the art. A preferred materialfor the casing is titanium although stainless steel, milled steel,nickel-plated milled steel and aluminum are also suitable. The casingheader comprises a metallic lid having a sufficient number of openingsto accommodate the glass-to-metal seal/terminal pin feedthroughconnected to the cathode electrode 14 via tab 40 (FIG. 5). The anodeelectrode 12 is preferably connected to the case or the lid. Anadditional opening is provided for electrolyte filling. The casingheader comprises elements having compatibility with the other componentsof the electrochemical cell and is resistant to corrosion. The cell isthereafter filled with the electrolyte solution described hereinaboveand hermetically sealed such as by close-welding a stainless steel plugover the fill hole, but not limited thereto.

The cell of the present invention can also be constructed in acase-positive design. Further, the flat-folded, multi-plate electrodeassembly of the present invention is readily adaptable to secondary,rechargeable electrochemical chemistries.

It is appreciated that various modifications to the invention conceptsdescribed herein may be apparent to those skilled in the art withoutdeparting from the spirit and the scope of the present invention definedby the hereinafter appended claims.

What is claimed is:
 1. A battery, which comprises:a) an anode comprisingan anode current collector having a plurality of anode connectorportions bridging between adjacent anode contact portions of the anodecurrent collector provided with an anode active material contactedthereto to thereby provide anode plates connected by the anode connectorportions, wherein the anode connector portions are of an increasinglygreater length from a first anode plate progressing to a last anodeplate; b) a cathode electrode comprising a cathode current collectorhaving a plurality of cathode connector portions bridging betweenadjacent cathode contact portions of the cathode current collectorprovided with a cathode active material contacted thereto to therebyprovide cathode plates connected by the cathode connector portions,wherein the cathode connector portions are of an increasingly greaterlength from a first cathode plate progressing to a last cathode plate;c) a separator disposed between the anode electrode and the cathodeelectrode juxtaposed one on top of the other to provide a flat foldableanode and cathode electrode overlay with a first plate of one of theanode electrode and the cathode electrode folded on top of a secondplate of the other of the anode electrode and the cathode electrode suchthat a first connector portion of the one folded cathode plate or anodeplate is of a length greater than the thickness of the other of theanode electrode or the cathode electrode to thereby provide a firstfolded electrode configuration and wherein the first folded electrodeconfiguration is foldable on top of the next anode and cathode electrodeoverlay with the connector portions of the anode electrode and thecathode electrode intermediate the first folded electrode configurationand the next anode and cathode electrode overlay having lengthssufficient to provide for the combined thickness of the subsequentfolded electrode configuration consisting of the first folded electrodeconfiguration and the next anode electrode and cathode electrode overlayand wherein the respective successive connector portions connectingbetween the subsequent folded electrode configuration and the successiveanode plates and the successive cathode plates of the electrode overlayare of a progressively greater length to accommodate the ever increasingthickness of the following folded electrode configuration foldable tothe last anode plate and the last cathode plate of the electrodeoverlay; and d) an electrolyte activating and operatively associatingthe anode electrode and the cathode electrode.
 2. The battery of claim 1wherein the first plate of the one of the anode electrode and thecathode electrode folded on top of a second plate of the other of theanode electrode and the cathode electrode is an anode plate.
 3. Thebattery of claim 1 wherein the anode electrode consists of one moreanode plate than the cathode electrode consists of cathode plates. 4.The battery of claim 1 wherein the anode electrode is a unitary member.5. The battery of claim 1 wherein the cathode electrode is a unitarymember.
 6. The battery of claim 1 wherein the cathode active material isselected from the group of a carbonaceous material, a fluorinatedcarbon, a metal, a metal oxide, a metal sulfide and a mixed metal oxide,and mixtures thereof.
 7. The battery of claim 1 wherein the cathodeelectrode further comprises at least one of a binder material and aconductive additive.
 8. The battery of claim 7 wherein the bindermaterial is a fluoro-resin power.
 9. The battery of claim 7 wherein theconductive additive is selected from the group consisting of carbon,graphite powder, acetylene black and metallic powder selected from thegroup consisting of titanium, aluminum, nickel and stainless steel, andmixtures thereof.
 10. The battery of claim 1 wherein the anode electrodeis comprised of a Group IA metal.
 11. The battery of claim 1 wherein theelectrolyte activating the anode electrode and the cathode electrodecomprises an ion-forming alkali metal salt dissolved in a nonaqueoussolvent, and wherein the alkali metal of the salt is the same as thealkali metal comprising the anode electrode.
 12. The battery of claim 1housed inside of a casing selected from the group consisting oftitanium, stainless steel, milled steel, nickel-plated milled steel andaluminum, and mixtures thereof.